Days Between Dates Calculator

Duration comparison
Item	Value
0 days	0
0 weeks	0
0.0 months	0
0.0 years	0

How to use this tool

Enter the start date. Pick or type the start date. Today's date is set as the default.
Enter the end date. Pick or type the end date. You can set a future or past date - results work in both directions.
Adjust options. Toggle "Include end date" if you want both endpoints counted. Toggle "Weekdays only" to exclude weekends from the count.
Read the results. Read the calendar years/months/days span, exact day count, whole weeks, and approximate total months and years.

How days between dates are calculated

The calculator converts each date to a UTC timestamp (midnight), subtracts the start from the end, and divides by the number of milliseconds in a day (86,400,000). The result is always a whole number of days; partial days are not possible since the inputs are calendar dates without a time component.

The Include end date toggle adds one day to account for both endpoints. For example, from January 1 to January 3: without inclusion = 2 days (Jan 1 to Jan 2); with inclusion = 3 days (Jan 1, Jan 2, Jan 3).

Weekdays only counts Monday through Friday between the two dates, excluding Saturdays and Sundays. It does not exclude public holidays; use the Working Days Calculator for that.

Understanding the units

Days: exact whole-day count, may be negative if end is before start.
Weeks: whole weeks only (floor of days ÷ 7). Fractional weeks are not shown.
Calendar difference: complete calendar years and months, followed by the remaining days. Dates near the end of a month are clamped to the last valid day in a shorter month; for example, January 31 to February 28 is one calendar month in a non-leap year.
Approx. months and years: total days divided by the average lengths of 30.4375 days per month (365.25 ÷ 12) and 365.25 days per year. These rounded totals are useful for comparison, but they are not calendar-month or calendar-year counts.

Common date difference examples

From	To	Days	Weeks
Jan 1	Feb 1 (same year)	31	4
Jan 1, 2023	Jul 1, 2023	181	25
Jan 1, 2024	Jul 1, 2024	182	26
Jan 1	Jan 1 (next year, non-leap)	365	52
Jan 1	Jan 1 (next year, leap)	366	52
Monday	Friday (same week, exclusive)	4	0
Monday	Friday (same week, inclusive)	5	0

Famous date calculation examples

Event	Date difference
Apollo 11 launch to moon landing	July 16–20, 1969 (4 calendar days; time of day is not counted)
World War II (Europe)	Sept 1, 1939 – May 8, 1945 (2,076 days)
Berlin Wall standing	Aug 13, 1961 – Nov 9, 1989 (10,315 days / 28.2 years)
Titanic sinking to wreck discovery	April 15, 1912 – Sept 1, 1985 (73 years)
Y2K bug scare	Jan 1, 2000 00:00:00 UTC (25+ years ago as of 2025)

DST caveat

Daylight Saving Time (DST) transitions can cause "23-hour days" or "25-hour days" in local time zones:

Spring forward (DST start): March 10, 2024, 2:00 AM -> 3:00 AM (skipped 1 hour). The day has only 23 hours.
Fall back (DST end): Nov 3, 2024, 2:00 AM -> 1:00 AM (repeated 1 hour). The day has 25 hours.

This calculator compares calendar dates, so a DST transition never changes its whole-day count. Clock-time durations across a DST boundary can differ by an hour from the day count multiplied by 24; use a time-zone-aware calculation when the exact elapsed hours matter.

Practical uses

Age calculator: Use the Age Calculator for an age breakdown from a date of birth to a chosen date.
Project planning: Calculate elapsed time between project start and deadline.
Legal/contract deadlines: Verify whether 30-day notice periods or statute of limitations have passed.
Historical research: Compute time spans between historical events (e.g., "How long did the Roman Empire last?").
Relationship milestones: "How many days since we met?" or "How long until our anniversary?"

Frequently asked questions

How do I count the number of days between two dates?

Subtract the earlier date from the later date. Each 24-hour period equals one day. This calculator does that automatically - just pick two dates and the result appears instantly. Enable "Include end date" to count both endpoints (e.g., Jan 1 to Jan 3 with end date included = 3 days; without = 2 days).

What does "include end date" mean?

By default the count is exclusive of the end date, like counting from a start day to (but not including) the end day. This is the standard mathematical interval [start, end). Enabling "include end date" switches to [start, end], adding one day to the total. Use this when you want to count both the first and last day - for example, when calculating the duration of a trip that starts and ends on those days.

Are the month and year totals calendar exact?

The Calendar difference result uses complete calendar years and months, then shows remaining days. Approx. months and Approx. years are day-based totals using an average month of 30.4375 days and year of 365.25 days.

How do I calculate working days between two dates?

Enable the "Weekdays only" toggle. The calculator counts Monday through Friday, excluding Saturdays and Sundays. Public holidays are not excluded - for that, use the Working Days Calculator tool.

What if my end date is before my start date?

The result will be negative, indicating the end date is in the past relative to the start date. The weekdays count is always shown as a positive number regardless of order.